System and method for supporting partition-aware routing in a multi-tenant cluster environment

ABSTRACT

A system and method can support partition-aware routing in a multi-tenant cluster environment. An exemplary method can support one or more tenants within the multi-tenant cluster environment. The method can associate each of the one or more tenants with a partition of a plurality of partitions. The method can then associate each of the plurality of partitions with one or more nodes of a plurality of nodes, each of the plurality of nodes being associated with a leaf switch of a plurality of switches, the plurality of switches comprising a plurality of leaf switches and a plurality of root switches. Finally, the method can generate one or more linear forwarding tables, the one or more linear forwarding tables providing isolation between the plurality of partitions, wherein each of the plurality of nodes is associated with a partitioning order.

CLAIM OF PRIORITY

This application claims the benefit of priority to U.S. Provisional Application titled “SYSTEM AND METHOD FOR SUPPORTING PARTITION-AWARE ROUTING IN A MULTI-TENANT CLUSTER ENVIRONMENT”, Application No. 62/073,615, filed Oct. 31, 2014; U.S. Provisional Application titled “SYSTEM AND METHOD FOR SUPPORTING PARTITION-AWARE ROUTING IN A MULTI-TENANT CLUSTER ENVIRONMENT”, Application No. 62/074,443, filed Nov. 3, 2014; U.S. Provisional Application titled “SYSTEM AND METHOD FOR SUPPORTING PARTITION-AWARE ROUTING IN A MULTI-TENANT CLUSTER ENVIRONMENT”, Application No. 62/076,961, filed Nov. 7, 2014; and U.S. Provisional Application titled “SYSTEM AND METHOD FOR SUPPORTING PARTITION-AWARE ROUTING IN A MULTI-TENANT CLUSTER ENVIRONMENT”, Application No. 62/133,187, filed Mar. 13, 2015, which applications are herein incorporated by referenced.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

FIELD OF INVENTION

The present invention is generally related to computer systems, and is particularly related to a multi-tenant cluster environment.

BACKGROUND

Multi-tenancy promises high utilization of available system resources and helps maintain cost-effective operations for service providers. However, multi-tenant high-performance computing (HPC) infrastructures bring unique challenges, both associated with providing performance isolation to the tenants, and achieving efficient load-balancing across the network fabric.

SUMMARY

A system and method can support partition-aware routing in a multi-tenant cluster environment. An exemplary method can support one or more tenants within the multi-tenant cluster environment. The method can associate each of the one or more tenants with a partition of a plurality of partitions. The method can then associate each of the plurality of partitions with one or more nodes of a plurality of nodes, each of the plurality of nodes being associated with a leaf switch of a plurality of switches, the plurality of switches comprising a plurality of leaf switches and a plurality of root switches. Finally, the method can generate one or more linear forwarding tables, the one or more linear forwarding tables providing isolation between the plurality of partitions, wherein each of the plurality of nodes is associated with a partitioning order.

In accordance with an embodiment, in multi-tenant HPC systems, each tenant can experience predictable network performance, unaffected by the workload of other tenants.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an illustration of a multi-tenant cluster environment, in accordance with an embodiment.

FIG. 2 shows an illustration of a tree topology in a network environment, in which an embodiment of the present disclosure can be practiced.

FIG. 3 shows an illustration of routing in a multi-tenant cluster environment, in which an embodiment of the present disclosure can be practiced.

FIG. 4 shows an illustration of routing in a multi-tenant cluster environment, in which an embodiment of the present disclosure can be practiced.

FIG. 5 shows an illustration of supporting partition-aware routing in a multi-tenant cluster environment, in accordance with an embodiment.

FIG. 6 shows an illustration of supporting partition-aware routing in a multi-tenant cluster environment, in accordance with an embodiment.

FIG. 7 shows an illustration of supporting partition-aware routing in a multi-tenant cluster environment, in accordance with an embodiment.

FIG. 8 shows an illustration of supporting partition-aware routing in a multi-tenant cluster environment, in accordance with an embodiment.

FIG. 9 shows an illustration of a method for supporting partition-aware routing in a multi-tenant cluster environment, in accordance with an embodiment.

DETAILED DESCRIPTION

In the following detailed description, the invention will be illustrated by way of example and not by way of limitation in the figures of the accompanying drawings. It should be noted that references to “an” or “one” or “some” embodiment(s) in this disclosure are not necessarily to the same embodiment, and such references mean at least one. While specific implementations are discussed, it is understood that the specific implementations are provided for illustrative purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without departing from the scope and spirit of the invention.

Common reference numerals are used to indicate like elements throughout the drawings and detailed description; therefore, reference numerals used in a figure may or may not be referenced in the detailed description specific to such figure if the element is described elsewhere.

The following description of the invention uses an Infiniband™ (IB) network as an example for a high performance network. It will be apparent to those skilled in the art that other types of high performance networks can be used without limitation. The following description also uses the fat-tree topology as an example for a fabric topology. It will be apparent to those skilled in the art that other types of fabric topologies can be used without limitation.

InfiniBand™

InfiniBand™ (IB) is an open standard lossless network technology developed by the InfiniBand™ Trade Association. The technology is based on a serial point-to-point full-duplex interconnect that offers high throughput and low latency communication, geared particularly towards HPC applications and datacenters.

The InfiniBand™ Architecture (IBA) supports a two-layer topological division. At the lower layer, IB networks are referred to as subnets, where a subnet can include a set of hosts interconnected using switches and point-to-point links. At the higher level, an IB fabric constitutes one or more subnets, which can be interconnected using routers.

Within a subnet, hosts are connected using switches and point-to-point links. Additionally, there is one master management entity, the subnet manager (SM), which resides on a designated subnet device in the subnet. The subnet manager is responsible for configuring, activating and maintaining the IB subnet. Additionally, the subnet manager (SM) can be responsible for performing routing table calculations in an IB fabric. Here, for example, the routing of the IB network aims at proper load balancing between all source and destination pairs in the local subnet.

Through the subnet management interface, the subnet manager exchanges control packets, which are referred to as subnet management packets (SMPs), with subnet management agents (SMAs). The subnet management agents reside on every IB subnet device. By using SMPs, the subnet manager is able to discover the fabric, configure end nodes and switches, and receive notifications from SMAs.

Generally, all other subnet managers, excepting the master subnet manager, act in standby mode for fault-tolerance. In a situation where a master subnet manager fails, however, a new master subnet manager is negotiated by the standby subnet managers. The master subnet manager also performs periodic sweeps of the subnet to detect any topology changes and reconfigure the network accordingly.

Furthermore, hosts and switches within a subnet can be addressed using local identifiers (LIDs), and a single subnet can be limited to 49151 LIDs. Besides the LIDs, which are the local addresses that are valid within a subnet, each IB device can have a 64-bit global unique identifier (GUID) that is burned into its non-volatile memory. A GUID can be used to form a global identifier (GID), which is an IB layer three (L3) address. A GID can be created by concatenating a 64-bit subnet identifier (ID) with the 64-bit GUID to form an IPv6-like 128-bit address. For example, different port GUIDs can be assigned to the ports connected to the IB fabric.

The SM can calculate routing tables (i.e., the connections/routes between each pair of nodes within the tree) at network initialization time. Furthermore, the routing tables can be updated whenever the topology changes, in order to ensure connectivity and optimal performance. During normal operations, the SM can perform periodic light sweeps of the network to check for topology changes. If a change is discovered during a light sweep or if a message (trap) signaling a network change is received by the SM, the SM can reconfigure the network according to the discovered changes.

For example, the SM can reconfigure the network when the network topology changes, such as when a link goes down, when a device is added, or when a link is removed. The reconfiguration steps can include the steps performed during the network initialization. Furthermore, the reconfigurations can have a local scope that is limited to the subnets, in which the network changes occurred. Also, the segmenting of a large fabric with routers may limit the reconfiguration scope.

Multi-Tenancy in IB Systems

From the networking perspective, multi-tenancy, via partitioning, can provide high utilization of network resources and help maintain cost effective operation for the service providers. However, multi-tenant infrastructures also impose several important security issues, one of the most challenging being associated with providing performance isolation for tenants. Each tenant should be provided with predictable network performance, unaffected by the workload of other tenants in the system. Network isolation in IB systems can be provided through partitioning.

In accordance with an embodiment, partitions are logical groups of ports such that the members of a group can only communicate to other members of the same group. At host channel adapters (HCAs) and switches, packets can be filtered using the partition membership information to enforce isolation. Packets with invalid partitioning information can be dropped as soon as the packets reach an incoming port. In multitenant IB systems, partitions can be used to create tenant clusters. With partition enforcement in place, a node cannot communicate with other nodes that belong to a different tenant cluster. In this way, the security of the system can be guaranteed even in the presence of compromised or malicious tenant nodes.

IB routing generally can be based on linear forwarding tables (LFTs) stored in the switches. The LFTs are calculated by the subnet manager (SM) without considering partitioning information. Hence, an intermediate network link might carry traffic belonging to different partitions. This sharing of intermediate links can lead to partition interference. As a result, tenants experience non-predictable network performance. Furthermore, the balancing features of the routing algorithm are also affected in a partitioned subnet. This is because even though the links crossing partition boundaries are not utilized for user traffic, these links are routed the same way as other functional links (and hence considered in the balancing). Degraded balancing may result in reduced effective bandwidth and sub-optimal network utilization.

IB generally provides Quality of Service (QoS) features that can be used to guarantee each partition a share of the available bandwidth, regardless of the nodes in the other partitions. The bandwidth guarantees are then provided by assigning each partition an available differentiated traffic class, called service level (SL). Each SL is then mapped to one of the available fifteen virtual lanes (VLs) on the link according to the SL to VL mapping table.

A problem can arise when assigning SLs to the partitions because the system can only utilize 15 VLs to create distinct partitions in the network, while an IB network in general can have a large number of partitions (e.g., each port can be a member of up to 32,768 partitions). Furthermore, it is common to support only nine VLs (including one reserved for subnet management) in existing IB hardware. Moreover, as SLs are a scarce resource, it may be desirable to leave as many of them as possible free for other purposes, e.g. to provide fault tolerance or service differentiation in the network.

IB Architecture

In accordance with an embodiment, IB is an open standard lossless network technology developed by IBTA (InfiniBand Trade Association). The technology defines a serial point-to-point full-duplex interconnect that offers high throughput and low latency communication. An IB network can consist of one or more subnets interconnected using routers. Within a subnet, hosts are connected using switches and point-to-point links. Within each IB subnet, there can be one master management entity, the subnet manager (SM)—residing on any designated subnet device—that configures, activates, and maintains the IB subnet.

Through the subnet management interface, the SM exchanges control packets, called subnet management packets (SMPs), with the subnet management agents (SMAs) that reside on every IB device. Using SMPs, the SM is able to discover the fabric, configure end nodes and switches, and receive notifications from SMAs. The SM can also perform periodic light sweeps of the subnet to detect any topology changes and reconfigure the network accordingly.

In accordance with an embodiment, Intra-subnet routing in an IB network can be based on LFTs stored in the switches. The LFTs are calculated by the SM according to the routing mechanism in use. In a subnet, all HCA ports on the end nodes and all switches are addressed using local identifiers (LIDs). Each entry in an LFT consists of a destination LID (DLID) and an output port. Only one entry per LID in the table is supported. When a packet arrives at a switch, its output port is determined by looking up the DLID in the forwarding table of the switch. The routing is deterministic as packets take the same path in the network between a given source-destination pair (LID pair).

In accordance with an embodiment, partitioning is a security mechanism supported by IB to provide for isolation of logical groups of systems sharing a network fabric. Each HCA port on a node in the fabric can be a member of one or more partitions. Partition memberships are managed by a centralized partition manager, which can be part of the SM. The SM can configure partition membership information on each port as a table of 16-bit partition keys (P Keys). The SM can also configure switches and routers with the partition enforcement tables containing P Key information associated with the LIDs.

In accordance with an embodiment, for the communication between nodes, Queue Pairs (QPs) and End-to-End contexts (EECs) can be assigned to a particular partition, except for the management Queue Pairs (QP0 and QP1). The P Key information can then be added to every IB transport packet sent. When a packet arrives at an HCA port or a switch, its P Key value can be validated against a table configured by the SM. If an invalid P Key value is found, the packet is discarded immediately. In this way, communication is allowed only between ports sharing a partition.

An example of IB partitions is shown in FIG. 1, which shows an illustration of a multi-tenant cluster environment, in accordance with an embodiment. In the example shown in FIG. 1, nodes A-E, 101-105, use the InfiniBand fabric, 100, to communicate, via the respective host channel adapters 111-115. The nodes A-E are arranged into partitions, namely partition 1, 110, partition 2, 120, and partition 3, 130. Partition 1 comprises node A 101 and node D 104. Partition 2 comprises node A 101, node B 102, and node C 103. Partition 3 comprises node C 103 and node E 105. Because of the arrangement of the partitions, node D 104 and node E 105 are not allowed to communicate as these nodes do not share a partition. Meanwhile, for example, node A 101 and node C 103 are allowed to communicate as these nodes are both part of partition 2, 120.

In accordance with an embodiment, IB is a layered architecture in which each physical link can be divided into multiple virtual links using the VLs. Each VL can have its own buffering, flow-control and congestion management resources. QoS can be provided through a set of differentiated traffic classes, the SLs. The SL represents the class of service a packet can receive in the network. Each SL is mapped to a VL on a link based on the configured SL to VL mapping table. IB supports up to 16 VLs. However, the last VL is reserved for the subnet management traffic and is generally not used by user applications.

Fat-Tree (FTree) Topologies and Routing

In accordance with an embodiment, some of the IB based HPC systems employ a fat-tree topology to take advantage of the useful properties fat-trees offer. These properties include full bisection-bandwidth and inherent fault-tolerance due to the availability of multiple paths between each source destination pair. The initial idea behind fat-trees was to employ fatter links between nodes, with more available bandwidth, as the tree moves towards the roots of the topology. The fatter links can help to avoid congestion in the upper-level switches and the bisection-bandwidth is maintained.

FIG. 2 shows an illustration of a tree topology in a network environment, in which an embodiment of the present disclosure can be practiced. As shown in FIG. 2, one or more end nodes 201-204 can be connected in a network fabric 200. The network fabric 200 can be based on a fat-tree topology, which includes a plurality of leaf switches 211-214, and multiple spine switches or root switches 231-234. Additionally, the network fabric 200 can include one or more intermediate switches, such as switches 221-224.

Also as shown in FIG. 2, each of the end nodes 201-204 can be a multi-homed node, i.e., a single node that is connected to two or more parts of the network fabric 200 through multiple ports. For example, the node 201 can include the ports H1 and H2, the node 202 can include the ports H3 and H4, the node 203 can include the ports H5 and H6, and the node 204 can include the ports H7 and H8.

Additionally, each switch can have multiple switch ports. For example, the root switch 231 can have the switch ports 1-2, the root switch 232 can have the switch ports 3-4, the root switch 233 can have the switch ports 5-6, and the root switch 234 can have the switch ports 7-8.

In accordance with an embodiment, the fat-tree routing mechanism is one of the most popular routing algorithm for IB based fat-tree topologies. The fat-tree routing mechanism is also implemented in the OFED (Open Fabric Enterprise Distribution—a standard software stack for building and deploying IB based applications) subnet manager, OpenSM.

The fat-tree routing mechanism aims to generate LFTs that evenly spread shortest-path routes across the links in the network fabric. The mechanism traverses the fabric in the indexing order and assigns target LIDs of the end nodes, and thus the corresponding routes, to each switch port. For the end nodes connected to the same leaf switch, the indexing order can depend on the switch port to which the end node is connected (i.e., port numbering sequence). For each port, the mechanism can maintain a port usage counter, and can use this port usage counter to select a least-used port each time a new route is added.

As mentioned above, in a partitioned subnet, nodes that are not members of a common partition are not allowed to communicate. Practically, this means that some of the routes assigned by the fat-tree routing algorithm are not used for the user traffic. The problem arises when the fat tree routing mechanism generates LFTs for those routes the same way it does for the other functional paths. This behavior can result in degraded balancing on the links, as nodes are routed in the order of indexing. As routing is done oblivious to the partitions, fat-tree routed subnets, in general, provide poor isolation among partitions.

FIG. 3 shows an illustration of routing in a multi-tenant cluster environment, in which an embodiment of the present disclosure can be practiced. More specifically, FIG. 3 elaborates on the issues of degraded load balancing and poor isolation.

FIG. 3 shows a 2-level fat-tree topology with four switches, root switches 325-326, and leaf switches 320-321, and six end nodes, nodes A-F, 301-306, in three overlapping partitions. Partition 1 comprises node B 302 and node C 303. Partition 2 comprises node A 301, node C 303, node D 304, and node F 306. Finally, partition 3 comprises node D 304 and node E 305.

In accordance with an embodiment, partitions 1 and 3 are entirely confined within the leaf switches 320 and 321 (i.e., single leaf switch partitions), respectively. Because of this, the communication between nodes in partitions 1 and 3 takes place through their corresponding leaf switches without moving traffic to the root switches, 325 or 326. When this topology is routed by the fat-tree routing mechanism, the routes towards the nodes connected to the leaf switches 320 and 321 are assigned root switches so the inter-leaf switch flows can reach their destination. For load-balancing, the routes towards A and C are assigned root switch 325 (shown as link p on the figure), while the root switch 326 routes traffic towards node B (shown as link q on the figure). Similarly for the leaf switch 321, traffic towards nodes D and F, in interleaf switch partition 2 are routed via the root switch 325 (shown as link r on the figure), and the traffic towards node E is routed via root switch 326 (shown as link s on the figure).

In accordance with an embodiment, an end port selection on the root switches is shown as the small circle with the node identifier in the figure. As the routing is done without considering the partitioning information (using the fat-tree routing mechanism), the paths in the subnet are not balanced properly. Links p and r are oversubscribed, while no intra-leaf switch flow will ever use link q or s. The routes assigned towards nodes B and E are not utilized (except for the relatively low management traffic) as both nodes cannot receive any communication from outside their leaf switches, due to their partitioning. This balancing issue also occurs in fat-trees when a partition's communication is restricted to only some of the levels in the topology.

Referring now to FIG. 4, which shows an illustration of routing in a multi-tenant cluster environment, in which an embodiment of the present disclosure can be practiced. More specifically, FIG. 4 elaborates on the issues associated with poor isolation within a fat-tree.

FIG. 4 shows a 2-level fat-tree topology with four switches, root switches 425-426, and leaf switches 420-421, and eight end nodes, nodes A-G, 401-408. As well, the end nodes are divided into two partitions. Partition 1 comprises node A 401, node B 402, node G 407, and node H 408. Partition 2 comprises node C 403, node D 404, node E 405, and node F 406.

Each of the partitions has two nodes connected to each of the two leaf switches. The fat-tree routing mechanism assigns downward ports on the root switches 425 and 426, as shown in the figure. Because of the nature of the fat-tree routing mechanism, each root switch routes traffic towards nodes belonging to both partitions, which provides for poor isolation, something that is not desired in a partitioned environment. For example, the traffic towards nodes A and C is routed on the shared link p. The sharing of intermediate links between nodes of different partitions can cause interference among them. Despite that the network has adequate resources at the root level to provide complete isolation among partitions, the fat-tree routing mechanism does not provided for the desired isolation.

Partition-Aware Fat-Tree (pFTree) Routing

In accordance with an embodiment, a partition-aware fat-tree routing mechanism (variously referred to herein as pFTree) can achieve desired objectives associated with multi-tenancy in an IB network. For example, the pFTree mechanism can provide for well-balanced linear forwarding tables for fat-tree topologies by distributing routes evenly across the links in the tree. Additionally, while maintaining routes on the links balanced, pFTree can remove contention between paths belonging to different partitions.

In accordance with an embodiment, a pFTree mechanism can use partitioning information about the subnet to ensure that the nodes in a partition receive a predictable network performance that is unaffected by the workload running in other partitions. In a situation where the topology does not have enough links available to provide partition isolation at each level (without compromising on the load-balancing), the pFTree can assign VLs to reduce the impact of contention.

In accordance with an embodiment, the pFTree mechanism can work recursively to set up LFTs on all relevant switches for the LIDs associated with each end node. This is shown in the below pseudo code (referred to herein as listing 1):

1: for each sw ε leafSwitches[ ] do 2:  Load partitioning information 3:  Filter leaf-switch only partitions 4:  Sort end nodes in partitioning specific order 5:  for each cn ε endNodes[ ] do 6:   Get lid of cn 7:   Get partition key of the cn.hca_port 8:   Set LFT[lid] ← cn:hca port on sw 9: ROUTEDOWNGOINGBYASCENDING( ) on sw 10:  end for 11: end for 12: ASSIGNVIRTUALLANES( )

In accordance with an embodiment, the ROUTEDOWNGOINGBYASCENDING( ) is exemplified in the below pseudo code (referred to herein as listing 2):

1: Get least-loaded ports from sw.UpGroups[ ] as uplist[ ] 2: selected port ← upList.get_port_max_guid( ) 3: for each port in upList[ ] do 4:  r_sw ← port:get_remote_switch( ) 5:  if r_sw is marked with partition_key then 6:   selected_port ← port 7:   break 8:  end if 9: end for 10: if r_sw is not marked then 11:   Mark it with partition_key in DWN direction 12: end if 13: Set LFT[lid] ← selected_port on r_sw 14: ROUTEUPGOINGBYDESCENDING( ) on sw 15: ROUTEDOWNGOINGBYASCENDING( ) on r_sw

In accordance with an embodiment, the ROUTEUPGOINGBYDESCENDING( ) is exemplified in the below pseudo code (referred to herein as listing 3):

1: Get least-loaded ports from sw.DownGroups[ ] as dwnlist[ ] 2: selected port ← dwnList.get_port_max_guid( ) 3: for each port in dwnList[ ] do 4:  r_sw ← port:get_remote_switch( ) 5:  if r_sw is marked with partition_key then 6:   selected_port ← port 7:   break 8:  end if 9: end for 10: if r_sw is not marked then 11:   Mark it with partition_key in UP direction 12: end if 13: Set LFT[lid] ← selected_port on r_sw 14: ROUTEUPGOINGBYDESCENDING( ) on r_sw

In accordance with an embodiment, the ASSIGNVIRTUALLANES( ) is exemplified in the below pseudo code (referred to herein variously as listing 4):

1: vlanes_needed ← 1 2: max_vlanes ← get_max_lanes( ) 3: strict ← get_is_strict( ) 4: for each partition in partition_tbl do 5: check if any intermediate communication link in this partition share a switch with a partition that has not been assigned a virtual lane 6: if require a separate vl then 7:  if vlanes_needed = max_vlanes and strict = false then 8:   vlanes_needed ← 1 9:  else 10:   error: routing failed 11:   return 12:  end if 13:  vlanes_needed++ 14:  partition.vlane ← vlanes_needed 15:  end if 16: end for

In accordance with an embodiment, after filtering out single-leaf switch partitions (i.e., those partitions that can communicate entirely within a single leaf switch), for each leaf switch, the mechanism can sort connected end nodes in a partitioning specific order (line 4 of above listing 1) (e.g., via each partition having a unique partitioning order number). This ordering can assist with ensuring that the nodes are routed according to their partitions, considering the available number of up-going ports at a leaf switch. The pFTree mechanism can then call a function, such as ROUTEDOWNGOINGBYASCENDING (line 9 of above listing 1), and move up in the tree to select a port at the next level to route the LID, as shown in the listing 2.

In accordance with an embodiment, the port selection is based on a least number of already assigned routes. This can help ensure that the load is spread across the available paths. However, when several ports are available with the same load, the function can iterate through these least-loaded ports and select a port which is connected to a switch that is already marked with the partition key of the node being routed (lines 3-9 of listing 2). If no switch is marked (which can indicate that the first node for this partition is being routed), the system can default to the selection of the port with the highest globally unique identifier (GUID) (line 2 of listing 2). When a switch is selected the first time for a partition, it is marked in the downward direction with the partition key (line 11 of listing 2).

In accordance with an embodiment, after the down-going port is set for a LID at a switch, the mechanism can assign upward ports for it on all the connected downward switches by descending down the tree calling (ROUTEUPGOINGBYDESCENDING of listing 3). Again, the selection of the up-going port can first be based on the load criterion and then on the partition marking of the remote switches, in the upward direction. The process can then be repeated by moving up to the next level in the tree until all LFTs are set. Note that a switch can be marked with multiple partition keys. The pFTree mechanism can maintain a table for each switch, storing the count of routed nodes for each partition. This counter can be used to decide the selection of the port if several switches with marked partitions are available to route a node. The switch with the maximum number of already routed nodes for a partition can be selected.

In accordance with an embodiment, once the routing tables are generated, keeping the partition isolation criteria, the mechanism can move on to check if some of the links are being used for flows towards nodes in different partitions. For those cases, the mechanism can assign VLs to the interfering partitions to provide isolation. An example of a VL assignment mechanism is shown in Listing 4.

In accordance with an embodiment, the VL assignment mechanism can iterate through the partitions and check if any intermediate communication link used by the nodes in the partition shares an intermediate link with another partition that has not been assigned a separate VL. If such a situation is encountered, a new VL can be assigned. The pFTree routing mechanism can support two modes for the VL selection: a strict mode and a normal mode.

In accordance with an embodiment, in the strict mode, if number of required VLs for pFTree routing exceeds the available VLs in the system, the routing can fail (line 10 of listing 4).

In accordance with an embodiment, in the normal mode, the algorithm can restart assigning VLs to the partitions from VL₁ (line 8 of listing 4).

In accordance with an embodiment, an efficient partition-aware routing mechanism for IB based fat-tree networks (variously referred to as pFTree) is provided. The pFTree mechanism can provide network-wide isolation of partitions for fat-tree topologies. In addition, pFTree produces well balanced LFTs for the switches. Given adequate network resources, pFTree can isolate partitions solely at the physical link level. For instance, if a fat-tree has two non-overlapping equal sized partitions, pFTree can divide the intermediate network links into two equally sized logical sub-networks based on the routing itself. Furthermore, if the network does not have enough available resources to provide complete partition isolation, pFTree can employ a complementary VL based isolation scheme that works in conjunction with the physical isolation.

In accordance with an embodiment, the pFTree routing mechanism aims to achieve two main objectives. Firstly, the mechanism can generate well-balanced LFTs for fat-tree topologies by distributing routes evenly across the links in the tree. Secondly, while maintaining routes on the links balanced, pFTree removes contention between paths belonging to different partitions. The pFTree can use partitioning information about the subnet and ensures that the nodes in a partition receive a predictable network performance, unaffected by the workload running in other partitions. If the topology does not have enough links available to provide partition isolation at each level (without compromising on the load-balancing), the pFTree can use VLs to reduce the impact of contention.

In accordance with an embodiment, the pFTree mechanism can work recursively to set up LFTs on all relevant switches for the LIDs associated with each end node. After filtering out single leaf switch partitions, for each leaf switch, the mechanism can sort connected end nodes in a partitioning specific order. This ordering ensures that the nodes are routed according to their partitions, considering the available number of up-going ports at a leaf switch. The port selection at each level can be based on the least number of already assigned routes to make sure that the load is spread across the available paths. However, when several ports are available with the same load, the function iterates through these least-loaded ports and selects a port which is connected to a switch that is already marked with the partition key of the node being routed. If no switch is marked (i.e., routing for the first node for a particular partition), pFTree can fall to the default selection of the port with the highest globally unique identifier (GUID). When a switch is selected the first time for a partition, the switch can be marked with the partition key. In this way the mechanism can help ensure that, given enough paths are available for balancing, the nodes belonging to one partition will be routed through the same switches and corresponding links. Once the routing tables are generated, keeping the partition isolation criteria, the mechanism can move on to check if some of the links are being used for flows towards nodes in different partitions. For those cases, the mechanism can assign VLs to the interfering partitions to provide isolation.

Referring now to FIGS. 5-8, which are illustrations of supporting partition-aware routing in a multi-tenant cluster environment, in accordance with an embodiment.

In accordance with an embodiment, the port selection mechanism in the pFTree routing is shown in FIGS. 5-8 by way of a simple section of an oversubscribed fat-tree network.

Referring now to FIG. 5, which shows a 2-level fat-tree topology with four switches, root switches 525-526, and leaf switches 520-521, and eight end nodes, nodes A-G, 501-508. As well, the end nodes are divided into two partitions. Partition 1 comprises node A 401, node D 504, node G 507, and node H 508. Partition 2 comprises node B 502, node C 503, node E 505, and node F 506.

In accordance with an embodiment, as shown in FIG. 5, the example section consists of two leaf switches (520 and 521), each connected to four end nodes and two switches at the next level above the leaf switches, i.e., root switches (525 and 526). The variables for down and max, which represent a number of assigned routes in the downward direction, and maximum number of nodes that can be routed to ensure proper balancing on each link, respectively, are also indicated in the figure.

In accordance with an embodiment, given there are two up-going ports at each leaf switch with four end nodes to route, each of the up-links should route two end-nodes down to ensure that the links are balanced (i.e., max=2).

In accordance with an embodiment, for leaf switch 520, the routing of the first two nodes, node A and node B, is shown in FIG. 6. The routing mechanism can select root switch 525 to route traffic towards node A and mark the switch with node A's partition key, shown as “(Partition 1)” in the figure. Similarly, for node B, root switch 526 can be selected and marked with node B's partition key, shown as “(Partition 2)” in the figure. The variable down is also updated to count a single routed node on each of the two downward links.

In accordance with an embodiment, for nodes C and D, the switch, which is already marked with the corresponding partition key, can be selected, as given in FIG. 7. The resultant routes flow towards nodes belonging to the first partition, i.e., nodes A and D, with the same link through root switch 525. Similarly, the nodes of the second partition, i.e., nodes B and C can be routed downwards through root switch 526. This separation of routes avoid interference between the traffic flows of the two partitions. Note that the number of nodes routed downwards on each links does not exceed the max variable, which means that the routing is still balanced.

Finally, in accordance with an embodiment, FIG. 8 shows routing for the end nodes connected to the leaf switch 521. Here also, as the second-level switches are already marked with the partition keys from the first leaf switch routing, the corresponding switches can be selected to route each of the nodes, i.e., nodes E, F, G, and G. As shown in the figure, the final routing can isolate the two partitions by dividing the intermediate network links into two equal sized logical sub-networks based on the routing.

FIG. 9 shows an illustration of a method for supporting partition-aware routing in a multi-tenant cluster environment, in accordance with an embodiment. The exemplary method 900 can begin at step 901 supporting one or more tenants within the multi-tenant cluster environment. At step 902, the exemplary method can associate each of the one or more tenants with a partition of a plurality of partitions. The method can, at step 903, associate each of the plurality of partitions with one or more nodes of a plurality of nodes, each of the plurality of nodes being associated with a leaf switch of a plurality of switches, the plurality of switches comprising a plurality of leaf switches and a plurality of switches at other levels. Finally, at step 904, the method can generate one or more linear forwarding tables, the one or more linear forwarding tables providing isolation between the plurality of partitions, wherein each of the plurality of nodes is associated with a partitioning order.

Many features of the present invention can be performed in, using, or with the assistance of hardware, software, firmware, or combinations thereof. Consequently, features of the present invention may be implemented using a processing system (e.g., including one or more processors).

Features of the present invention can be implemented in, using, or with the assistance of a computer program product which is a storage medium (media) or computer readable medium (media) having instructions stored thereon/in which can be used to program a processing system to perform any of the features presented herein. The storage medium can include, but is not limited to, any type of disk including floppy disks, optical discs, DVD, CD-ROMs, microdrive, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or optical cards, nanosystems (including molecular memory ICs), or any type of media or device suitable for storing instructions and/or data.

Stored on any one of the machine readable medium (media), features of the present invention can be incorporated in software and/or firmware for controlling the hardware of a processing system, and for enabling a processing system to interact with other mechanism utilizing the results of the present invention. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems and execution environments/containers.

Features of the invention may also be implemented in hardware using, for example, hardware components such as application specific integrated circuits (ASICs). Implementation of the hardware state machine so as to perform the functions described herein will be apparent to persons skilled in the relevant art.

Additionally, the present invention may be conveniently implemented using one or more conventional general purpose or specialized digital computer, computing device, machine, or microprocessor, including one or more processors, memory and/or computer readable storage media programmed according to the teachings of the present disclosure. Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will be apparent to those skilled in the software art.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention.

The present invention has been described above with the aid of functional building blocks illustrating the performance of specified functions and relationships thereof. The boundaries of these functional building blocks have often been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Any such alternate boundaries are thus within the scope and spirit of the invention.

The foregoing description of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments. Many modifications and variations will be apparent to the practitioner skilled in the art. The modifications and variations include any relevant combination of the disclosed features. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications that are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents. 

What is claimed is:
 1. A method for supporting partition-aware routing in a multi-tenant cluster environment, comprising: supporting one or more tenants within the multi-tenant cluster environment; associating each of the one or more tenants with a partition of a plurality of partitions; associating each of the plurality of partitions with one or more nodes of a plurality of nodes, each of the plurality of nodes being associated with a leaf switch of a plurality of switches, the plurality of switches comprising a plurality of leaf switches and a plurality of switches at other levels; and generating one or more linear forwarding tables, the one or more linear forwarding tables providing isolation between the plurality of partitions; wherein each of the plurality of nodes is associated with a partitioning order.
 2. The method of claim 1, wherein generating one or more linear forwarding tables comprises: ordering, for each of the plurality of leaf switches, the plurality of nodes according to the partitioning order associated with each node, resulting in an order of nodes; and routing, in the order of nodes, the plurality of end nodes, the routing comprising: selecting at least one down-going port and at least one up-going port for each node, the selecting being based upon at least a factor selected from the group consisting of a load criterion, and a partition marking of a switch.
 3. The method of claim 2, further comprising: prior to ordering the plurality of nodes according to the partition order associated with each node, filtering for single-leaf switch partitions.
 4. The method of claim 1, wherein providing for isolation between the plurality of partitions comprises: ensuring that communication between nodes associated with different partitions do not share a route between switches of the plurality of switches.
 5. The method of claim 1, further comprising: allowing the plurality of switches and the plurality of nodes to be arranged in a tree topology.
 6. The method of claim 5, wherein the tree topology is a fat tree topology.
 7. The method of claim 1, wherein the multi-tenant cluster environment comprises an InfiniBand network.
 8. A system supporting partition-aware routing in a multi-tenant cluster environment, the system comprising: one or more microprocessors; and a processor, running on the one or more microprocessors, wherein the processor operates to perform steps comprising: supporting one or more tenants within the multi-tenant cluster environment; associating each of the one or more tenants with a partition of a plurality of partitions; associating each of the plurality of partitions with one or more nodes of a plurality of nodes, each of the plurality of nodes being associated with a leaf switch of a plurality of switches, the plurality of switches comprising a plurality of leaf switches and a plurality of switches at other levels; and generating one or more linear forwarding tables, the one or more linear forwarding tables providing isolation between the plurality of partitions; wherein each of the plurality of nodes is associated with a partitioning order.
 9. The system of claim 8, wherein generating one or more linear forwarding tables comprises: ordering, for each of the plurality of leaf switches, the plurality of nodes according to the partitioning order associated with each node, resulting in an order of nodes; and routing, in the order of nodes, the plurality of end nodes, the routing comprising: selecting at least one down-going port and at least one up-going port for each node, the selecting being based upon at least a factor selected from the group consisting of a load criterion, and a partition marking of a switch.
 10. The system of claim 9, the steps further comprising: prior to ordering the plurality of nodes according to the partition order associated with each node, filtering for single-leaf switch partitions.
 11. The system of claim 8, wherein providing for isolation between the plurality of partitions comprises: ensuring that communication between nodes associated with different partitions do not share a route between switches of the plurality of switches.
 12. The system of claim 8, wherein the plurality of switches and the plurality of nodes to be arranged in a tree topology.
 13. The system of claim 12, wherein the tree topology is a fat tree topology.
 14. The system of claim 8, wherein the multi-tenant cluster environment comprises an InfiniBand network.
 15. A non-transitory machine readable storage medium having instructions stored thereon for supporting partition-aware routing in a multi-tenant cluster environment that when executed cause a system to perform steps comprising: supporting one or more tenants within the multi-tenant cluster environment; associating each of the one or more tenants with a partition of a plurality of partitions; associating each of the plurality of partitions with one or more nodes of a plurality of nodes, each of the plurality of nodes being associated with a leaf switch of a plurality of switches, the plurality of switches comprising a plurality of leaf switches and a plurality of switches at other levels; and generating one or more linear forwarding tables, the one or more linear forwarding tables providing isolation between the plurality of partitions; wherein each of the plurality of nodes is associated with a partitioning order.
 16. The non-transitory machine readable storage medium of claim 15, wherein generating one or more linear forwarding tables comprises: ordering, for each of the plurality of leaf switches, the plurality of nodes according to the partitioning order associated with each node, resulting in an order of nodes; and routing, in the order of nodes, the plurality of end nodes, the routing comprising: selecting at least one down-going port and at least one up-going port for each node, the selecting being based upon at least a factor selected from the group consisting of a load criterion, and a partition marking of a switch.
 17. The non-transitory machine readable storage medium of claim 16, the steps further comprising: prior to ordering the plurality of nodes according to the partition order associated with each node, filtering for single-leaf switch partitions.
 18. The non-transitory machine readable storage medium of claim 15, wherein providing for isolation between the plurality of partitions comprises: ensuring that communication between nodes associated with different partitions do not share a route between switches of the plurality of switches.
 19. The non-transitory machine readable storage medium of claim 15, the steps further comprising: allowing the plurality of switches and the plurality of nodes to be arranged in a tree topology.
 20. The non-transitory machine readable storage medium of claim 19, wherein the tree topology is a fat tree topology. 